1. Field of the Invention
The present invention relates to an exhaust pipe structure for a vehicle and, more particularly, to an exhaust pipe structure for a vehicle, which can reduce damage at the time when the vehicle is subjected to a rear end offset collision.
2. Description of the related art
On a vehicle mounted with an engine in a front part thereof, an exhaust pipe collected by an exhaust manifold extends to the rear part of the vehicle through a floor tunnel under the lower surface in the vehicle body center, and communicates with the outside air via a muffler disposed in the rear end part of the vehicle. To suppress the output loss of engine caused by exhaust resistance, a sufficient muffler volume must be secured. Therefore, on the vehicle designed with an emphasis on running performance, the muffler is often provided on both right and left sides of the rear end part of the vehicle.
The exhaust pipe of such a dual muffler type vehicle generally branches on the rear of a fuel tank under a rear seat, and is connected to the right and left mufflers via right and left branch pipes. As the layout of the branch pipes, a Y-shaped or T-shaped layout in which the branch pipes are provided at the right and left symmetrically with respect to the vehicle center is generally used (refer to JP9-86193A).
In the case in which a vehicle is subjected to a collision from the rear by another running vehicle, that is, in the case of rear end collision, a full overlap collision and an offset collision are assumed. For example, the former corresponds to a collision of a following vehicle with a vehicle stopping in a traffic lane, and the latter corresponds to a collision of a following vehicle with a vehicle stopping on the shoulder of a road or contact at a road merging point or at the time of lane change. In the case of the offset collision, a rear end collision from the side rear of the driver's seat or from the slantwise rear is assumed.
In the case in which the aforementioned dual muffler type vehicle is subjected to a rear end offset collision, even in a slight degree of collision, a high load is applied to the muffler positioned on the collision side of the rear end part of vehicle body. Thereby, the whole of the exhaust pipe is pushed out to the vehicle front side together with the muffler, so that a primary silencer or a secondary catalyst on the upstream side of the exhaust pipe may be damaged. Especially on the vehicle provided with the branch pipes having a Y-shaped layout, a force such as to push out the exhaust pipe to the vehicle front side via the branch pipes acts strongly, so that the parts arranged on the upstream side are influenced greatly. Also, for the T-shaped branch pipe layout, a branch part may be damaged by the concentration of bending stresses.